Within the oil and gas industry, it is frequently necessary to determine the mass flow rate of a single- or multi-phase fluid stream flowing through a pipeline. For example, in a multi-phase produced stream containing water, natural gas, and liquid hydrocarbons, the mass flow rate may be used to determine the final volumes and the resulting value of each product stream.
Separate gas and liquid flow meters are traditionally used to determine the total mass, energy and/or volumetric flow rate of multi-phase fluid streams. However, multiple meters, production separators and other related equipment are typically required to divide the products into single phase streams prior to measurement since conventional meters in the oil and gas industry cannot accurately determine the mass flow rate of multi-phase fluid streams. Systems of this type, particularly offshore and in deep water applications, require huge expenditures to provide this capability on-board offshore platforms of various types. There are newer technologies being used to determine the mass flow rates of produced multiphase streams offshore (microwave, gamma radiation, etc.), but they have an unacceptably high measurement uncertainty unless the stream being measured is close to being all gas or all liquid. These systems are being used in order to avoid the capital costs associated with offshore platforms even though their measurement performance is very poor. Due to the large volumes involved and the relatively high values of oil and natural gas, even small inaccuracies introduced by the flow meter can lead to significant losses within a relatively short period of time.
Therefore, there is a need in the industry for systems and methods that will accurately determine the mass flow rate of multi-phase fluid streams without first requiring that the fluid stream be divided into separate streams (natural gas, liquid hydrocarbon and water). There is also a need for a single system that can collect all of the measurements needed to calculate the mass flow rate, thereby improving efficiency, reducing capital costs, eliminating the need for an associated production platform and minimizing the amount of space needed for the system. Note that for existing or new systems using high uncertainty measurement systems, the invention could be used to correct the mass flow rate indications from those systems to values much closer to actual, greatly reducing the uncertainties associated with these various technologies.